Hot gas generator employing rotary turbine

ABSTRACT

A hot gas generator includes a combustion chamber the heated gases from which drives a turbine the combustion chamber being provided with air/fuel mixture for burning therein by a compressor driven by the turbine. A second compressor is provided to supply dilution fluid in the form of an air/fuel mixture. The dilution fluid together with the heated gases leaving the combustion chamber are maintained at a speed which is higher than the flame speed and the combustion of the air/fuel mixture which constitutes the dilution fluid takes place in a second combustion chamber which includes a divergent portion whereby the velocity of the gases is reduced below the flame speed.

United States Patent 1191 1111 3,740,948 Kellett June 26, 1973 HOT GASGENERATOR EMPLOYING 2,679,137 5/1954 Probert (SO/39.65

ROTARY TURBINE 1,700,592 1/1929 Loepsinger 431/346 Inventor: EricKellett, London, England C.A.V. Limited, Birmingham, England Filed: Apr.8, 1971 Appl. No.: 132,429

Assignee:

Foreign Application Priority Data Apr. l4, 1970 Great Britain 17,561/70References Cited UNITED STATES PATENTS 5/1971 Schmidt 60/261 7/1962Seifferlein 60/261 4/1958 Ogilvie .1 (JO/39.65

Primary Examiner-Carlton R. Croyle Assistant ExaminerWarren OlsenAttorney-Holman & Stern [57] ABSTRACT A hot gas generator includes acombustion chamber the heated gases from which drives a turbine thecombustion chamber being provided with air/fuel mixture for burningtherein by a compressor driven by the turbine. A second compressor isprovided to supply dilution fluid in the form of an air/fuel mixture.The dilution fluid together with the heated gases leaving the combustionchamber are maintained at a speed which is higher than the flame speedand the combustion of the air/fuel mixture which constitutes thedilution fluid takes place in a second combustion chamber which includesa divergent portion whereby the velocity of the gases is reduced belowthe flame speed.

1 Claim, 1 Drawing Figure HOT GAS GENERATOR EMPLOYING ROTARY TURBINEThis invention relates to hot gas generators of the kind comprising acombustion chamber, a first compressor for delivering an air/fuelmixture to the combustion chamber, a second compressor for deliveringdilution fluid to the combustion chamber, a turbine coupled to saidcompressors for driving same, said turbine being driven by the heatedgases leaving said combustion chamber.

The object of the invention is to provide such a generator in a form inwhich for a given size of generator and a given inlet temperature, theheat release can be increased.

According to the invention in a generator of the kind specified thedilution fluid is an air/fuel mixture and there is disposed downstreamof the turbine a second combustion chamber having a divergent portion,the arrangement being such that the velocity of the hot gases after themixing of dilution fluid therewith is higher than the flame speed of theair/fuel mixture constituting the dilution fluid, the velocity of thegases entering the second combustion chamber falling therein to avelocity lower than the flame speed thereby allowing combustion of theair/fuel mixture to take place within the second combustion chamber.

One example of a hot gas generator in accordance with the invention willnow be described with reference to the accompanying drawing which showsa sectional side elevation of the generator.

Referring to the drawing there is provided a first compressor having aninlet 11 and an outlet 12. The inlet 11 communicates with a conduitcommunicating with the atmosphere and formed in the wall of the conduitis an aperture 27 through which gaseous fuel can be admitted to the airflowing to the compressor.

There is also provided a second compressor 13 having an inlet 14 and anoutlet 15. The inlet 14 communicates with the atmosphere and a fuelsupply nozzle 16 is disposed adjacent the inlet.

The compressors are each provided with a rotor, the rotors being mountedupon a common shaft 17 which is coupled to the rotor of a turbine 18.The turbine includes an inlet 19 and an outlet 20 which opens into adiverging combustion chamber 21.

Also provided is a combustion chamber 22 which is surrounded by a casing23. The combustion chamber 22 at one end mounts a burner 24 and theburner is coupled to the outlet 12 of the first compressor. Projectinginto the combustion chamber is an electrical ignitor 25 and thecombustion chamber downstream of the burner is provided with apertures26 through which dilution fluid from the space defined intermediate thecombustion chamber 22 and its casing 23 can pass. The dilution fluidconsists of air/fuel mixture derived from the outlet 15 of the firstcompressor. The outlet 15 for this purpose being connected to theaforesaid annular space.

In operation, the air/fuel mixture leaving the first compressor isignited by the ignitor 25 and burns within the combustion chamber 22.The temperature of the heated gases is reduced in known manner by thedilution fluid which enters the combustion chamber by way of theapertures 26 and the heated gases then pass through the turbine 18 intothe combustion chamber 21. The heated gases leaving the combustionchamber 22 drive the turbine and this in turn drives the compressors sothat once started the apparatus is self sustaining providing fuel issupplied to the burner.

In order to obtain a greater heat release fuel is mixed with the airflowing through the second compressor but in order to prevent this fuelburning until it has passed through the turbine, it is arranged that thevelocity of the dilution fluid and the gases leaving the combustionchamber 22 are higher than the flame speed of the air/fuel mixtureconstituting the dilution fluid. In view of this no combustion will takeplace until the gases enter the combustion chamber 21. This combustionchamber diverges and therefore the velocity of the gases falls below theflame speed. Once the velocity has fallen to a value below the flamespeed spontaneous combustion takes place and the fuel which flowsthrough the nozzle 16 burns within the combustion chamber 21.

In the manner described above a high heat release can be obtained for agiven size of generator and for a given temperature of the hot gasesentering the turbine, than can be achieved in the case where all thefuel is burnt within the combustion chamber 22.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

l. A hot gas generator comprising a combustion chamber, an air/fuelmixture burner disposed in the combustion chamber, a first compressorfor delivering air/fuel mixture to said burner, a second compressor fordelivering air as dilution fluid to the combustion chamber for coolingthe heated gases produced by the burner, a turbine coupled to saidcompressors for driving same, said turbine being driven by the heatedgases leaving the combustion chamber, means for mixing fuel with the airflowing through said second compressor, so that the dilution fluid is anair/fuel mixture, and a second combustionchamber disposed downstream ofthe turbine, said second combustion chamber having a divergent portion,the generator being so arranged that the velocity of the hot gases afterthe mixing of the dilution fluid therewith is higher than the flamespeed of the air/fuel mixture constituting the dilution fluid, thevelocity of the gases entering the second combustion chamber fallingtherein to a velocity lower than the flame speed thereby allowingcombustion of the air/fuel mixture to take place within the secondcombustion chamber. v

1. A hot gas generator comprising a combustion chamber, an air/fuelmixture burner disposed in the combustion chamber, a first compressorfor delivering air/fuel mixture to said burner, a second compressor fordelivering air as dilution fluid to the combustion chamber for coolingthe heated gases produced by the burner, a turbine coupled to saidcompressors for driving same, said turbine being driven by the heatedgases leaving the combustion chamber, means for mixing fuel with the airflowing through said second compressor, so that the dilution fluid is anair/fuel mixture, and a second combustion chamber disposed downstream ofthe turbine, said second combustion chamber having a divergent portion,the generator being so arranged that the velocity of the hot gases afterthe mixing of the dilution fluid therewith is higher than the flamespeed of the air/fuel mixture constituting the dilution fluid, thevelocity of the gases entering the second combustion chamber fallingtherein to a velocity lower than the flame speed thereby allowingcombustion of the air/fuel mixture to take place within the secondcombustion chamber.